High-Speed Milling of Hardened Mold Steel P20 with Minimum Quantity Lubrication

Strong thermal-mechanical coupling and rapid tool failure easily occur in the milling process of hardened steel with solid end mills. This work investigates the effectiveness of minimum quantity lubrication (MQL) during high-speed milling of hardened mold steel. Three kinds of spraying modes were designed in the experiment. They are namely the spraying ways to the flank face (MQL-F), to the rake face (MQL-R) and to the rake and flank faces (MQL-FR). The cutting forces, tool wear, and chips when using the MQL modes and compressed air cooling mode (CAIR-F) were compared, and the wear mechanism and lubrication mechanism were further analyzed. The results showed that the tool wear values and milling forces of several MQL modes were significantly lower than those with CAIR-F. The milling force and tool wear values were successively reduced using MQL-R, MQL-F, and MQL-FR, with better lubrication of the rake face resulting in a smaller curvature radius for the chip. Abrasion wear, adhesion/attrition wear, and flaking/chipping were the main wear mechanisms. The MQL-FR method was the optimal method of the MQL modes. It could effectively reduce the cutting contact stress and unit cutting energy, and obviously reduced wear phenomena such as adhesion and chipping.

Automated summary

This study investigates the effectiveness of minimum quantity lubrication (MQL) during high-speed milling of hardened mold steel, showing that the MQL-R, MQL-F, and MQL-FR modes successively reduce tool wear values and milling forces, with MQL-FR being the optimal method.